Urethral catheters are medical devices having an elongate shaft for insertion into the urethra of a patient for inter alia drainage of the urine in the patient's bladder, use in treating cancer of the prostace or delivering a medicament. They may be for in-dwelling in the urethra for a number of days or for intermittent self-catherisation.
A fairly recent development in the field of urethral catheters has been the formation on the elongate shaft of a surface coating which exhibits a reduced friction when wetted to facilitate insertion into the urethra. The need for facilitating the insertion of the shaft into the urethra will be readily appreciated when one considers that the outer diameter of the shaft of a catheter is typically greater than the inner diameter of the urethra. In the coated catheter this is achieved by soaking the shaft in a wetting liquid such as sterile water or saline immediately prior to insertion to make the shaft surface slippery. Prior to the development of coated catheters the elongate shafts were simply formed by uncoated plastics tubing, for example of PVC, and to facilitate insertion of the shaft it was necessary to apply to the shaft a lubricant in the form of a jelly or the like which was rather cumbersome and time-consuming. As examples of friction reducing coatings suitable for application to a catheter shaft there may be mentioned the polyvinyl pyrrolidone (PVP) hydrophilic surface coatings made known in EP-B-0 093 093 and EP-B-0 217 771 (Astra AB).
It is important that the packaging used for catheters having friction-reducing surface coatings be such as to provide the catheter with a long shelf-life because the time that a urethral catheter is held in storage prior to use can be rather lengthy. To this end, the catheter packaging needs to ensure that the friction-reducing coating on the catheter is protected, for instance against the environment. The form that the package takes, however, is complicated if the catheter is to be stored after having been subjected to a sterilising process to alleviate the risk of infection of the urinary tract by the catheter as the package will need to maintain the sterile state of the catheter. Such pre-sterilisation of the catheter has the advantage that the catheter will not need to be sterilised after the catheter storage package is opened and is especially useful when the catheter is a disposable or single-use catheter. A typical pre-sterilising process for surface coated urethral catheters involves exposing the catheter to ethylene oxide gas.
Paper packaging has hitherto been proposed for storing a surface coated urethral catheter which is to be pre-sterilised by ethylene oxide gas because the gas can pass through a paper construction. Thereby, the catheter can be placed in the package and subsequently be exposed to the sterilising gas. To this end, it is conventional for the paper packaging to be formed from a paper construction in which the paper is grid-lacquered with polyethylene and welded around its edge to a laminate of, for example, polyethylene-polypropylene, polyethylene-polyetheylene terephthalate of possibly polyetheylene-nylon. A problem encountered with such paper packages, however, is that moisture can ingress into the package during storage. If moisture penetrates to the paper package, the catheter coating will become sticky leading to the coating becoming damaged, destroyed or mutilated through adherence of the coating to the paper component of the package.
WO96/30277 (Coloplast A/S) discloses a catheter storage package where the problem of adherence of coated catheters to paper packaging is solved by inserting a plastics material adjacent to the interior surface of the paper so that the catheter cannot come into direct contact with the paper. To still enable ethylene oxide gas to gain access to the catheter surface the plastics material is provided with a number of slits. The drawback of this type of catheter package, however, is that it needs a complicated manufacturing process because the dimensions of the slits in the plastics material have to be carefully regulated so that they do not permit contact of the catheter surface with the paper without in anyway hindering access of the sterilising gas.
WO97/47349 (Astra AB) proposes a solution to this drawback associated with packages of the type disclosed in WO96/30277 by placing a coated urethral catheter in an inner container formed from a material which is permeable to a sterilising agent such as ethylene oxide gas, exposing the inner container to the sterilising agent and then enclosing the inner container in an outer container which is formed from a material which prevents access of moisture to the inner container. This “double pack” arrangement keeps the coating of the catheter sterile and dry until it is required to be used thereby overcoming the problem of the catheter coating becoming sticky due to contact with moisture and then becoming damaged due to adherence with the packaging.
A drawback of the package disclosed in WO97/47349 and the other aforementioned packages is that they do not include a supply for wetting liquid for wetting of the catheter coating prior to use of the catheter. For instance, in the case of the package disclosed in WO96/30277 the catheter coating is wetted by partially opening the package and then introducing sterile water or saline solution into the enclosure containing the catheter. In the case of the package of WO97/47349, on the other hand, the catheter is removed from the package and then soaked in sterile water or saline. Further, a problem with all the above mentioned packages are that the user needs to have access to clean water.
WO97/26937 (Astra AB) discloses a package which includes a supply of sterile wetting liquid in combination with a coated catheter. In this package a coated bladder drainage catheter is positioned in a urine collection bag together with a sealed wetting liquid container, containing sterile wetting liquid. This arrangement is then exposed to ethylene oxide gas to sterilise the catheter and surfaces of the bag and container and subsequently enclosed in a moisture proof outer casing for storage. In use, the outer casing is removed and the wetting liquid container ruptured to release the sterile wetting liquid contained therein into the bag for the catheter to soak in for wetting of the surface coating. The duly wetted catheter is then projected through a removable section of the bag into the urethra with urine drained from the bladder being captured in the collection bag.
As will be appreciated by the foregoing, the development of the prior-art storage packages for a catheter having a friction-reducing surface coating has been, in the direction of keeping the coating dry during storage. The present invention is based on the insight that the real problem is not the coating coming into contact with moisture per se but more the cyclical effect of the coating coming into contact with moisture and then drying out.
WO98/19729 (Coloplast A/S) discloses a ready-to-use storage package. The storage package according to this publication is formed by wetting the hydrophilic coating of the catheter with a wetting liquid prior to its encapsulation in the storage package. The walls of the storage package are formed from a gas impermeable material which prevents drying out and keeps the hydrophilic coating wet and “ready-to-use”. However, in this ready-to-use package a very limited amount of wetting liquid is supplied. When the catheter is wetted before placing it in the storage package the amount or water is naturally limited only to the amount adopted by the hydrophilic surface, and even in the embodiment where the wetting liquid is supplied after the placement of the catheter in the package, the amount of wetting liquid is limited only to the amount needed for the preparation of the hydrophilic surface of the catheter.